Magnesium base alloy



Patented Nov. 12, 1940 UNITED. STATES MAGNESIUM BASE ALLOY John C. McDonald, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Michigan No Drawing. Application November 13, 1939, Serial No. 304,129

3 Claims.

The invention relates to magnesium base alloys.

It more particularly concerns alloys of this nature having improved physical properties such as a high degree of formability together with high tensile and yield strengths.

Magnesium alloys are being widely used in various structural and mechanical arts where a light weight metal is highly desirable, such as for use in making castings, forgings, and the like. However, the use of these alloys in the rolled form to'make sheet metal articles requiring forming operations, such as bending, drawing, or the like, has not progressed as rapidly due to the fact that w in general alloys of good formability, permitting -relatively sharp bends to be made without the article developing external cracks, usually have inferior characteristics as regards their tensile and yield strengths.

20 It is, accordingly, the principal object of the having good ductility, have exceptionally high yield and tensile properties, and thus are also very suitable for use in castings as well as in making wrought forms. Thespecific proportions of each alloying metal to be employed according to the 5 invention depends upon the use for which the alloy is intended. In general, the .lowelfjfi n, centages of alloying metals give'a greater degree of elongation, and thus increased ductility or formability, while the higher percentages of al- 0 loying ingredients give a product having better yield and tensile properties.

The following table compares some of the properties of rolled sheet metal made from my new alloy with the properties of a related parent quaternary alloy, and illustrates the improvement in yield and tensile strengths of the new alloy. In the table the per cent elongation represents a measure of the ductility or formability of the invention to provide a magnesium base alloy y Table N t d m A eel (1 Cold rolled pereen rema ernn e nesium) m eld Tensile Percent Yield Tensile Percent Ag Ce Cd Mn strength in strength in elongation strength in strength in elon tlon lbsJsq. in lbsJsq. in. in 2 inches lbs/sq. in. lbsJsq. in. in 2 nches t 30 which may be made into rolled sheet or the like possessing a sufiicient degree of ductility or formability to be sharply bent, drawn, or otherwise shaped, while having high tensile and yield 40 strengths.

Other objects and advantages will become apparent in the following description.

My invention resides in the discovery that a magnesium base alloy composed oi from 0.5 to 10 per cent of silver, 0.05 to 1 per cent of calcium, 1 to 15 per cent of cadmium, and from 0.1 to 3- per cent of manganese, the balancebeing substantially all magnesium, is endowed with the aforementioned properties. While the properties of excellent formability or ductility together with high tensile and yield strengths are manifest over the entire range of composition indicated, I have 4 found that in general the preferred combination of properties, such as the most desirable ductility for forming operations with high tensile and yield strengths, is obtained when the alloy contains from 3 to 6 per cent of silver, 0.1 to 0.3 per cent of calcium, 6 to 8 per cent of cadmium. and 1.5 to 2 per cent of manganese. Alloys containing high- 00 er percentages of alloying ingredients, while still The properties listed in the above table under the section headed by the term annealed" were obtained by first rolling the alloys at a temperature between about 600 to 800 F., and thereafter annealing them at various tempera- 40 tures through a temperature range of from 400 to 800 F. The properties selected for the table were those of the annealed specimens which exhibited the maximum elongation. The properties listed under the section headed cold-rolle 45 were obtained by subjecting specimens of the 9.1- loys which had been hot-rolled at a tempera-' ture of from 600 to 800 F. to additional rolling in the cold state to bring about a total reduction in thickness of from 2 to 10 per cent. The prop- 50 erties selected for the table were those of the cold-rolled specimens which showed the greatest tensile and yield strengths, while having at least a 1 per cent elongation in 2 inches. 55

By comparison of the properties listed in the above table, it will be observed that the coinbined properties of my new polynary alloy are superior to those of the parent quaternary alloys listed. Similarly, a marked improvement in the go properties is observed in other portions of the composition range.

While the new alloy is most useful in wrought form, such as sheets due to its formability characteristics, it may also be suitably used in making castings, forgings, extruded forms, and the like. It is further pointed out that my new alloy is amenable to solution and precipitation heat treatments which, accordingly, modify its properties.

The new alloy may be compounded in any of the ways known to the art, such as by adding the alloying ingredients to molten magnesium under a suitable flux. The flux should be substantially free of magnesium chloride if the calcium content is to be above 0.3 per cent. In those instances where an alloy is to be compounded containing less than 0.3 per cent of calcium, magnesium chloride may be present in the flux without exerting a deleterious effect, but in this case to 6 per cent of silver, from 0.1 to 0.3 per cent of calcium, 4 to 10 per cent of cadmium, and 1.5 to

2.5 per cent of manganese, the balance being magnesium.

3. A magnesium base alloy containing from 3 to 6 per cent of silver, from 0.1 to 0.3 per cent of calcium, 6 to 8 per cent of cadmium, and from 1.5 to 2 per cent of manganese, the balance being magnesium.

JOHN C. MCDONALD. 

